The easy answer is, very! The longer answer is that the AirZound can emit a deafening 115 decibel blast, which is loud enough to make even the worst of drivers or most inattentive of pedestrians stop in their tracks!
Here is a small clip which compares the horn from a Ford Fiesta car to my AirZound.
I have found that when I’ve used my AirZound people have to look around as they cannot believe that a bicycle made that noise…I have had a few weird looks in wing mirrors when people had to check. The majority of times I have used my AirZound it has been noticed and stopped someone from pulling out, or a situation from occurring.
One of the reasons I chose the AirZound compared to some other horns on the market was from one review, which said something along the lines of “My AirZound shocked someone so much that they hit their head on the roof of their car!”.